Speaking at a health committee hearing on childhood obesity, she said: “Broadly the evidence shows the higher the tax increase, the greater the effect.”

It comes after Health Secretary Jeremy Hunt was embroiled in a row over whether the PHE review, which was due to be published in July, had been suppressed, which the Department of Health (DoH) has denied.

Celebrity chef Jamie Oliver previously gave evidence to the committee calling for the Government to take “one strong hard action” and introduce a tax.

Dr Tedstone said PHE had reviewed data on the impact of taxation in five other countries and found “universally all of these assessments show that a tax does decrease purchases”.

But, while she said a tax could have a “halo effect”, Dr Tedstone said the full impact of a sugar tax was unclear.

She said: “We have just taken a general sense of modelling studies. What we don’t know, and Jamie talked about it yesterday, is how transitory the effect is.

“Everybody acknowledges there’s the moment of introducing that kind of tax has a big health halo effect and we don’t know how long that is sustained for.”

MPs also heard regulation of advertising and supermarket promotions were more urgent strategies than a tax on sugary products, and would have a wider effect.

A PHE spokesman said a date for publication date had yet to be set.

He said: “ Dr Tedstone was clear at the health select committee that there is no silver bullet solution to nation’s excessive sugar consumption.

“While Dr Tedstone said there is a role for fiscal measures in reducing how much sugar is consumed, she also said there are other actions - restricting advertising and promotion of sugary food and drink, and reformulating food and drink to have less sugar - we think would be more effective.”

Health Select Committee chairwoman Dr Sarah Wollaston said it was “completely disgraceful” that the report had not been released.

Dr Wollaston said: “This is evidence, and we are always told that evidence should be published in a transparent and timely manner, so there is no reason why this evidence shouldn’t be available to all the campaign groups and researchers that would like to be able to contribute to the Government’s obesity strategy.

“So we have made repeated calls for the Government and Public Health England to release it so we can all see it.”

She told BBC Radio 4’s Today programme: “The public has paid for this evidence review, it’s impartial - it has not been compiled by industry or anyone with a particular axe to grind - so let’s see it now, let’s publish it and then let all of us have the opportunity to see the evidence behind the thinking that will form the basis for the Government’s obesity strategy.”

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